Secondhand smoke takes a sizable toll on Americans’ health and productivity, particularly among black Americans, according to a recent study by researchers at the University of California San Francisco (UCSF).

Mining data collected between 2003 and 2006 by large government surveys, the researchers calculated that secondhand smoke kills 42,000 Americans each year, including nearly 900 infants. Secondhand smoke is linked to some of the same fatal illnesses caused by smoking, including heart and lung disease, and in babies, low birth weight, SIDS (sudden infant death syndrome) and respiratory distress syndrome.

Overall, the researchers found that yearly deaths from secondhand smoke accounted for about 600,000 years of potential life lost, or an average of 14.2 years per person. The price tag for that lost productivity loss equaled $6.6 billion in total — about $158,000 per death.

“One of the things our research tells us is that even though people are smoking less and more laws have been put in place to prevent smoking in public, the problem has not gone away,” says lead study author Dr. Wendy Max, a professor of health economics at the UCSF School of Nursing and co-director of the UCSF Institute for Health & Aging. “We still have a ways to go. These deaths from secondhand smoke tell us that individuals make choices about their smoking behaviors based on themselves, but they need to think about how their smoking impacts others.”

A previous study by the Centers for Disease Control and Prevention (CDC) also measured the health and economic impacts of secondhand smoking, using data from the California Environmental Protection Agency. The difference between the earlier study and the current one is that the CDC data were based on self-reports secondhand smoke exposure; the new study relied on an objective measure, called serum cotinine, to assess evidence of nicotine exposure in the blood.

“Some people may say they’re not exposed to secondhand smoke, but they forget about the smokey bus ride they took in the morning or when they walked through the park and someone was smoking near them,” says Max.

Compared with the CDC study, the UCSF researchers found lower rates of heart disease deaths from secondhand smoke, but higher rates of lung cancer deaths. The differences are to be expected given that more people are giving up smoking, Max says; lung cancer cases may be higher, since it takes longer for the risk of lung cancer to decline after quitting. The authors also reported more infant fatalities.

The researchers also found that black Americans were disproportionately exposed to secondhand smoke. Black men aged 45 to 64 had the highest rates of secondhand smoke exposure, followed by black men aged 20 to 44; black women aged 20 to 44 also had higher exposure than any other women. Further, black infants accounted for 24% to 36% of all infant deaths from secondhand smoke, although they represented only 13% of the total U.S. population

“It comes down to rates of exposure,” says Max. “Minorities are more likely to have higher smoking rates and work in places that are not smoke protected.”

The authors hope their findings will further highlight the importance of quitting smoking and increase funding for tobacco-control programs to protect both smokers and nonsmokers, especially those in vulnerable minority groups.

“It’s challenging to control what happens at home because we cannot tell people what to do in their homes, but I hope this motivates people to quit on their own,” says Dr. Max.